反推法高中英语教学中的重要性的几点浅析

如果一个学生高中三年都是同一个英语老师任教英语学科,而该英语老师在教学方法上一成不变,老调重弹,学生肯定会感到厌烦,对英语漫漫失去兴趣。如果老师时不时地改变一下自己的教学方法,例如经常采用反推教学法,效果肯定好多了。

高校工科专业课微信公众号建设——以“运动控制系统”精品课程为例

以同济大学"运动控制系统"精品课程建设为例,分析了大学工科专业课传统教学模式存在的弊端。结合智能手机和微信App的普及性,建设了专业课微信公众号,具备群发推送、在线对话、用户自主阅读3个功能。为便于用户自主阅读,利用自定义菜单,设计了微信公众号的主要板块及子项。通过教学实践中的3个典型案例,展示了课程公众号在实现课堂与实验室的翻转,改善教学效果,增进师生互动,提高学习兴趣,训练独立思考能力,树立科学精神等方面的成效。

Joint 3D traveltime calculation based on fast marching method and wavefront construction

3D traveltime calculation is widely used in seismic exploration technologies such as seismic migration and tomography. The fast marching method （FMM） is useful for calculating 3D traveltime and has proven to be efficient and stable. However, it has low calculation accuracy near the source, which thus gives it low overall accuracy. This paper proposes a joint traveltime calculation method to solve this problem. The method firstly employs the wavefront construction method （WFC）, which has a higher calculation accuracy than FMM in calculating traveltime in the small area near the source, and secondly adopts FMM to calculate traveltime for the remaining grid nodes. Due to the increase in calculation precision of grid nodes near the source, this new algorithm is shown to have good calculation precision while maintaining the high calculation efficiency of FMM, which is employed in most of the computational area. Results are verified using various numerical models.

Experimental Investigation on Basic Prototype of Solid Propellant Impulsive Microthrusters

A new type of impulsive microthruster and its measurement system were designed for the aim of testing the performance of a basic prototype of solid propellant impulsive microthruster. Two sets of tests were conducted. The tests show that the ignitor and the main charge of the microthruster match well, the dynamic and static capability of the test and measurement meets the test requirement and the result is creditable. The measured technical characteristics of the microthruster are that the ignition delay time is shorter than 0 3?ms, the total impulse is over 3?N·s, the operational time is shorter than 16?ms and the mass ratio of the thruster is 0 216.

A New Simulation Method for 3D Propellant Grain Burn Analysis of Solid Rocket Motor

Describes a new computer program (Regress-3D) to simulate the regression of complex 3D grain cavity and calculate the burning surface area. It has a large region of applicability in solid rocket motor design and has made new improvements compared with other available codes. User can easily and rapidly build his initial grain shapes and then obtain geometric information of his design. Considering with the calclulting results, redesigning can be performed as desire until reaching at the satisfied result. Advantages and disadvantages of this method are also discussed.

用政治正确讲一个好故事

北京时间2月25日,第91届奥斯卡奖举行颁奖礼,《绿皮书》获得最佳影片、最佳男配、最佳原创剧本三项大奖。观众们对这部电影的评价褒贬不一,一位黑人编剧Ira发推特吐槽:“《绿皮书》?我看更像是白皮书。”这条推特获得超过四万个赞,他接着说:“《撞车》正在目睹《绿皮书》取代它成为最逊的奥斯卡赢家。”美国主流媒体也是一片嘘声,《纽约时报》在推特上转发了一篇奥斯卡提名名单出炉时的长评,标题是《为什么奥斯卡持续沉迷于种族和谐的幻想之作?》。

APPLICATION OF HYBRID AERO-ENGINE MODEL FOR INTEGRATED FLIGHT/PROPULSION OPTIMAL CONTROL

The real-time capability of integrated flight/propulsion optimal control （IFPOC） is studied. An appli- cation is proposed for IFPOC by combining the onboard hybrid aero-engine model with sequential quadratic pro- gramming （SQP）. Firstly, a steady-state hybrid aero-engine model is designed in the whole flight envelope with a dramatic enhancement of real-time capability. Secondly, the aero-engine performance seeking control including the maximum thrust mode and the minimum fuel-consumption mode is performed by SQP. Finally, digital simu- lations for cruise and accelerating flight are carried out. Results show that the proposed method improves real- time capability considerably with satisfactory effectiveness of optimization.

Structure buckling and non-probabilistic reliability analysis of supercavitating vehicles

To perform structure buckling and reliability analysis on supercavitating vehicles with high velocity in the submarine,supercavitating vehicles were simplified as variable cross section beam firstly.Then structural buckling analysis of supercavitating vehicles with or without engine thrust was conducted,and the structural buckling safety margin equation of supercavitating vehicles was established.The indefinite information was described by interval set and the structure reliability analysis was performed by using non-probabilistic reliability method.Considering interval variables as random variables which satisfy uniform distribution,the Monte-Carlo method was used to calculate the non-probabilistic failure degree.Numerical examples of supercavitating vehicles were presented.Under different ratios of base diameter to cavitator diameter,the change tendency of non-probabilistic failure degree of structural buckling of supercavitating vehicles with or without engine thrust was studied along with the variety of speed.

MBDA R&T EFFORT ON PULSED AND CONTINUOUS DETONATION WAVE ENGINES

The continuous detonation wave engine（CDWE）can be considered to reduce the environmental conditions generated by pulsed detonation engine（PDE）while reducing the importance of initiation issue and simplifying some integration aspects.Specific experimental programs are performed by MBDA and Lavrentiev Institute to study CDWE operating mode and to address some key points for the feasibility of an operational rotating wave engine for space launcher.It is found that such engine can deliver impressive thrust in a very small package（275 daN for internal diameter of 50 mm and length of 100 mm,kerosene-oxygen engine）and that can be increased with the use of a diverging nozzle.Due to the geometry of the combustion chamber,a plug or aerospike nozzle seems to be the best design,the thrust vectoring capability of this engine（with the local change of the mass flow rate）being a way to solve the problem of attitude control.The heat fluxes are very high but located mostly near the injection wall.This point will help the gasification of the liquid component injected inside the combustion chamber.Some preliminary tests are performed to evaluate the capability of C/SiC composite materials to sustain the very severe mechanical environment generated by the rotating detonation waves.Beyond these first steps,a large scale ground demonstrator allowing to address all issues for a continuous detonation rocket engine using LH2/LOx mixture is designed by MBDA.As the first step toward the development of this large scale engine,a small scale demo is tested in Spring 2010.

Ignition characteristics and combustion performances of a LO_2/GCH_4 small thrust rocket engine

A 500 N model engine filled with LO2/GCH4 was designed and manufactured.A series of ignition attempts were performed in it by both head spark plug and body spark plug.Results show that the engine can be ignited but the combustion cannot be sustained when head spark plug applied as the plug tip was set in the gaseous low-velocity zone with thin spray.This is mainly because flame from this zone cannot supply enough ignition energy for the whole chamber.However,reliable ignition and stable combustion can be achieved by body spark plug.As the O/F ratio increases from 2.61 to 3.49,chamber pressure increases from 0.474 to 0.925 MPa and combustion efficiency increases from 57.8%to 95.1%.This is determined by the injector configuration,which cannot produce the sufficiently breakup of the liquid oxygen on the low flow rate case.

AN APPROXIMATE REASONING METHOD IN DEZERT-SMARANDACHE THEORY

With the increment of focal elements number in discernment framework,the computation amount in Dezert-Smarandache Theory (DSmT) will exponentially go up. This has been the bottleneck problem to block the wide application and development of DSmT. Aiming at this difficulty,in this paper,a kind of fast approximate reasoning method in hierarchical DSmT is proposed. Presently,this method is only fit for the case that there are only singletons with assignment in hyper-power set. These singletons in hyper-power set are forced to group through bintree or tri-tree technologies. At the same time,the assignments of singletons in those different groups corresponding to each source are added up respectively,in order to realize the mapping from the refined hyper-power set to the coarsened one. And then,two sources with the coarsened hyper-power set are combined together according to classical DSm Combination rule (DSmC) and Proportional Conflict Redistribution rule No. 5 (PCR5). The fused results in coarsened framework will be saved as the connecting weights between father and children nodes. And then,all assignments of singletons in different groups will be normalized respectively. Tree depth is set,in order to decide the iterative times in hierarchical system. Finally,by comparing new method with old one from different views,the superiority of new one over old one is testified well.

Influence of Firing Temperature on Properties of Gun Propellants

Initial firing temperatures play an important role on the combustion rate of propellant. In gun propellants, initial temperature is a key factor for both accuracy and safety. Ideally, the initial temperature of the propellant should not influence the ballistic properties of the round. Nevertheless, constant initial temperature coefficients can not be achieved easily. This work focuses on the influence of the firing temperature on the ballistic properties, the mechanical integrity and the sensitivity to impact of nitrocellulose based propellants. Combustion rates have been determined by closed vessel tests. Ballistic properties have been investigated by firing 5.56 cartridges. The propellants have been conditioned at temperatures ranging from -54 ℃ to ＋71 ℃ before firing. The largest temperature coefficient is observed at high temperatures. The temperature sensitivity of the peak pressure in the combustion chamber can not be fully explained by the results from the closed vessel test. The authors speculated that the mechanical behaviour of the propellant grains at low temperatures influences also the overall ballistic properties of the round. Impact tests with propellants conditioned at low and high temperatures permit to investigate their mechanical strength under extreme temperatures and to better understand the propellant performance during firing. Tests on aged propellants have been conducted as well.

500-ton LOX/Kerosene Engine Joint Test Achieved Success

Recently,the first gas generator-turbopump joint test for the 500-ton LOX/kerosene engine was completed with success.The engine developed independently by the Academy of Aerospace Liquid Propulsion Technology（AALPT）will be used for the heavy-lift rocket.The 500-ton LOX/kerosene engine has the thrust of the largest ever developed by China and in the foreseeable future.

ReTweeting Analysis and Prediction in Microblogs: An Epidemic Inspired Approach

Microblogs currently play an important role in social communication. Hot topics currently being tweeted can quickly become popular within a very short time as a result of retweeting. Gaining an understanding of the retweeting behavior is desirable for a number of tasks such as topic detection, personalized message recommendation, and fake information monitoring and prevention. Interestingly, the propagation of tweets bears some similarity to the spread of infectious diseases. We present a method to model the tweets' spread behavior in microblogs based on the classic Susceptible-Infectious-Susceptible (SIS) epidemic model that was developed in the medical field for the spread of infectious diseases. On the basis of this model, future retweeting trends can be predicted. Our experiments on data obtained from the Chinese micro-blogging website Sina Weibo show that the proposed model has lower predictive error compared to the four commonly used prediction methods.

Fault diagnosis of rocket engine ground testing bed with self-organizing maps(SOMs)

To solve the fault diagnosis problem of liquid propellant rocket engine ground testing bed,a fault diagnosis approach based on self-organizing map(SOM)is proposed.The SOM projects the multidimensional ground testing bed data into a two-dimensional map.Visualization of the SOM is used to cluster the ground testing bed data.The out map of the SOM is divided to several regions.Each region is represented for one fault mode.The fault mode of testing data is determined according to the region of their labels belonged to.The method is evaluated using the testing data of a liquid-propellant rocket engine ground testing bed with sixteen fault states.The results show that it is a reliable and effective method for fault diagnosis with good visualization property.

The Reliable and Intelligent Propulsion Pressurization System of the Long March 7 Launch Vehicle

The reliable and intelligent propulsion pressurization system is one of the key technologies of new Chinese generation launch vehicles; a high reliability design is an important guarantee for the success of launching. This paper analyzes the domestic and overseas liquid launch vehicles in the area of propulsion pressurization systems, based on comprehensive analysis, demonstrating the reliable and intelligent propulsion pressurization system of the Long March 7(Simplified as LM-7) has been raised. By applying a full chain redundancy design, setting proper pressure control bandwidth and control mode reconstruction under extreme fault conditions, the reliability and adaptability of the propulsion pressurization system has enhanced significantly. In addition, the complete system has been verified by the first two flights of LM-7.

Agricultural Higher Education for Sustainable Rural Development in Turkey

Agriculture in Turkey has been playing a significant role in Turkish economy and agricultural sectors are the most important provider of employment. Additionally, agriculture is major income source for farmers in rural areas and education level positively effects their income level and productivity. Agricultural faculties, institutions and agricultural extension services are mainly responsible for farmers＇ education in Turkey. The mission of agricultural education is to provide education for young people to prepare them for life and also work for rural community. Also, the agricultural education is responsible for the development of practical and theoretical knowledge of people in rural areas with disseminating information and new technologies. Basic field studies on the national qualifications framework for higher education of Turkey has been determined by a working group of deans formed by the CoHE under the Bologna process. Sixty programs on agriculture, forestry and fishery were identified at the faculties. A small working group formed among the deans of the agricultural faculties founded ZIDEK accreditation society to accredited programs at the agricultural faculties. Also a report was prepared by another working group to recommend worldwide programs to the agricultural faculties in Turkey. Mass media plays an important role for disseminating the agricultural innovations to rural areas. In this respect, the primary goal of Turkey is the improvement of welfare of farmers in order to sustain rural development. For this aim, handicraft training centers to diversify the rural economy, agricultural publication services of MoFAL distribute publications in order to disseminate information and new technologies, Widespread Education Project for Farmers （YAYCEP） has been started and within the scope of the project producers who live in rural areas, education and extension services and projects for woman farmers and other extension studies have been carried out under the Ministry of Food, Agriculture and Livestock in collaboration with 26 agricultural faculties in Turkey.

Comparison of the entrainment rate of debris flows in distinctive triggering conditions

Debris flows can be extremely destructive because they can increase in magnitude via progressive entrainment. In this paper, a total of 18landslide-type debris flows and 268 channelized debris flows in Wenchuan earthquake and Taiwan region, as well as other regions were collected to analyze the entrainment rate of debris flows in each triggering condition. Results show that there is a power relationship between volume of initial triggered mass and final deposited debris for landslide type debris flow. The debris flows during2008 and 2013 in Wenchuan earthquake-region have smaller entrainment rate than that from 2001 t02009 in Taiwan. The entrainment rate of debris flow events from 2001 to 2009 in Taiwan shows a decaying tendency as elapsed time. Comparison of the entrainment rate in the two earthquake-hit regions with other regions proves that entrainment rate has a close relation with major sediment availability and secondary rainstorm conditions.

Cubature Formula and Interpolation on the Cubic Domain

Several cubature formulas on the cubic domains are derived using the discrete Fourier analysis associated with lattice tiling, as developed in [10]. The main results consist of a new derivation of the Gaussian type cubature for the product Chebyshev weight functions and associated interpolation polynomials on [-1,1]^2, as well as new results on [-1, 1]^3. In particular, compact formulas for the fundamental interpolation polynomials are derived, based on n3/4 ＋ O（n^2） nodes of a cubature formula on [-1,1]^3.